This application claims priority of European Patent Application No. 99308191.8, which was filed on Oct. 18, 1999.
1. Field of the Invention
This invention relates to an optimised resonator filter, i.e. to a filter having dimensions optimised by a new method, and to a method for such dimension optimisation.
2. Description of Related Art
In wireless telecommunications at microwave frequencies, duplexers are used to transmit to and receive signals from an antenna. Currently available duplexers, which must have specified performance over a wide range of working temperatures, and required dimensions, carry material costs in the need to provide irises and tuning screws, and time costs in the need for a skilled person to tune the resonator before use.
A mode-matching technique for the derivation of the response of a filter, using the dimensions of a resonator cavity and dielectric puck, has been published by D Kajfez and P Guillon, Dielectric Resonators, Oxford MS: Vector Fields, 1990.
Computer programs to derive a full filter response, based on electromagnetic simulation techniques, are commercially available.
It has now been realised that such programs can be used to optimise the parameters of a filter, and that the results can be used in filter design.
It is an object of the invention to provide a resonator filter which does not need an iris or tuning or coupling screws but which still meets all technical requirements.
According to the invention a method of optimising the characteristics of a resonator filter comprising a dielectric puck in a conducting cavity characterised by deriving the diameter c and thickness j of the puck by a mode-matching technique; and optimising the diameter c and thickness j of the puck by electromagnetic simulation of a full filter response.
Also according to the invention a resonator filter comprising a puck of dielectric material within a conducting cavity, the diameter and thickness of the puck having been optimised by a method as set out above. Such a filter does not require tuning or coupling screws or an iris.